Treatment of zinc leach residue

Abstract

According to the present invention there is provided a method for treating a zinc leach residue comprising the steps of: adding the zinc leach residue and a sulfide material comprising copper and flux to a furnace having a molten bath therein; operating the furnace to produce a matte comprising copper and a slag comprising zinc; separating the matte from the slag; and recovering zinc from the slag. The method preferably comprises the additional step of recovering the copper and/or other precious metals such as silver and gold, from the matte.

1 . A method for treating a zinc leach residue comprising the steps of:
 adding the zinc leach residue and a sulfide material comprising copper and flux to a furnace having a molten bath therein;   operating the furnace to produce a matte comprising copper and a slag comprising zinc;   separating the matte from the slag; and   recovering zinc from the slag,   wherein the matte formed in the furnace comprises between about 40 to 75% copper.   
     
     
         2 . A method according to  claim 1 , further comprising the step of recovering the copper from the matte. 
     
     
         3 . A method according to  claim 1 , further comprising the step of treating the slag in a slag fumer or a slag fuming furnace to recover the zinc therefrom. 
     
     
         4 . A method according to  claim 1 , further comprising the step of treating the matte in a copper smelter to recover copper therefrom. 
     
     
         5 . A method according to  claim 4 , further comprising the step of recovering one or more precious metals from the final product of the smelter. 
     
     
         6 . A method according to  claim 5 , wherein the one or more precious metals comprise silver and gold. 
     
     
         7 . A method according to  claim 1 , wherein the furnace comprises a top-blown submerged-combustion lance (TSL) furnace. 
     
     
         8 . A method according to  claim 1 , wherein the furnace is operated at an oxygen partial pressure between about 10 −9.5  and 10 −7.5  atm. 
     
     
         9 . A method according to  claim 1 , wherein the furnace is operated at an oxygen partial pressure of about 10 −8.5  atm. 
     
     
         10 . A method according to  claim 1 , further comprising the step of adding air, oxygen, and/or oxygen-enriched air to the furnace. 
     
     
         11 . A method according to  claim 1 , wherein off gases from the furnace contain sulfur dioxide and are sent to an acid plant to produce sulfuric acid therefrom. 
     
     
         12 . A method according to  claim 1 , further comprising the step of adding one or more fluxes to the furnace. 
     
     
         13 . A method according to  claim 12 , wherein the one or more fluxes comprise silica, limestone, or another source of CaO. 
     
     
         14 . A method according to  claim 12 , wherein the fluxes and feed added to the furnace are selected or controlled to produce a slag with a zinc content in the range of about 10-20 wt. %. 
     
     
         15 . A method according to  claim 1 , wherein the slag has a CaO/SiO 2  ratio of between about 0.1 to 0.3. 
     
     
         16 . A method according to  claim 1 , wherein the slag has a ratio of SiO 2 /(Fe+Zn) of between about 0.6 to 0.8. 
     
     
         17 . A method according to  claim 1 , wherein the furnace is operated at a temperature of about 1100° C. to 1250° C. 
     
     
         18 . A method according to  claim 1 , further comprising the step of tapping the slag from the furnace in a molten state, wherein the molten slag is sent to a zinc fumer/zinc fuming furnace. 
     
     
         19 . A method according to  claim 1 , further comprising the step of tapping the matte from the furnace in a molten state, wherein the molten matte is sent to a copper smelter. 
     
     
         20 . A method according to  claim 1 , wherein the slag contains between about 5 to 25 wt. % zinc, when the slag leaves the furnace. 
     
     
         21 . (canceled) 
     
     
         22 . A method according to  claim 1 , wherein the copper-containing matte substantially digests any incoming precious metals with the exception of the zinc which reports preferentially to the slag phase. 
     
     
         23 . A method according to  claim 1 , wherein an inert slag or a glassy solid material comprising Fe, Ca, Al, and Si is formed as a by-product. 
     
     
         24 . Zinc, when recovered from a zinc leach residue by a method according to  claim 1 . 
     
     
         25 . Copper, when recovered from a sulfide material comprising copper and flux by a method according to  claim 1 . 
     
     
         26 . One or more precious metals comprising silver and/or gold when extracted from a zinc leach residue by a method as defined according to  claim 5 .